Ya'll are a smart bunch, how would you find these users?
Perhaps you are the one stop shop for the new to car ownership Gen Z, who didn't bother with dealing with a car until their job called them back to the office. They don't know what they need, what it will cost, where to get insurance, or how to avoid getting ripped off. A friend is currently going through this and finding it extremely stressful, as it was only a year ago that she even bothered to get her license as she didn't need a car until now.
Maybe you focus on the car buying experience for people who don't have great social skills to negotiate effectively and prefer not to deal with pushy salespeople (such as myself).
Maybe you are the best place to buy a car for the financially minded. You can give them an all in price for the car, including insurance, estimated fuel costs, gas, estimated repairs, subsidy availability, etc.
You would approach all of these users very differently.
Somebody like my mother in law who always leases a Toyota Corolla derivative from the same dealer? Somebody like me a few years back who was looking for a new Honda Fit but settled for a used one because I couldn’t find a new Fit? Somebody like me last month who got a 1996 Buick Park Avenue for his son from a shade tree mechanic because his son hates new cars and recent used car prices are insane (and not like Crazy Eddie!). Or the agricultural economist I know who picked up a Corvette for $35k at the peak of the 2008 crisis because he had cash and the dealer needed it? Or somebody who thinks Audis are the bees knees? (Yuck!). Or someone who can afford a new McLaren?
* There are a number of entrenched vendors in the space already for both new and used cars. * Car companies and dealerships are working to eliminate the "invoice vs MSRP" price gap that was people used to negotiate a car purchase. That doesn't mean that gap no longer exists, only that car companies and dealerships are just unwilling to negotiate below MSRP. They are only willing to negotiate the markup over MSRP, which in many cases is ludicrously high. * Some states have taken to legislating away the possibility of selling cars outside of dealer networks. Most with the intent to block Tesla, specifically, but they may also limit opportunities like what you are proposing.
There may be pockets of underserved consumers, but they are likely to have structural issues (low volume, high touch requirement, poor credit, legal concerns, etc.) that make them poor/undesirable targets for the established vendors. That usually translates to small market opportunity, limited upside availability, or both.
If you can figure out a way to completely disrupt the current model, you may be onto something. Tesla did that successfully with direct sales, and it worked until they started running into legal and legislative roadblocks precisely because of their success.